Modelling Turn-taking in a Simulation of Small Group Discussion

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Abstract

The organization of taking turns at talk is an important part of any verbal interaction
such as conversation, particularly in groups. Sociologists and psycholinguists have
been studying turn-taking in conversation through empirical and statistical analysis,
and identified some systematics in it. But to my knowledge no detailed computational
modelling of verbal turn-taking has yet been attempted.
This thesis describes one such attempt, for a simulation of small group discussion—
that is, engaged conversation in groups of up to seven participants, which researchers
have found to be much like two-person dialogues with overhearers. The group discussion
is simulated by a simple multi-agent framework with a blackboard architecture,
where each agent represents a participant in the discussion and the blackboard is their
channel of communication, or ‘environment’ of the discussion. Agents are modelled
with just a set of probabilistic parameters that give their likelihood of doing the various
turn-taking decisions in the simulation: when to talk, when to continue talking, when
to interrupt, when to give feedback (“uh huh”), and so on. The simulation, therefore,
consists of coordinating a one-at-a-time talk (symbolic talk) with speaker transitions,
hesitation, yielding or keeping the floor, and managing simultaneous talk which occurs
mostly around speaker transitions.
The turn-taking modelling considers whether participants are talking or not, and when
they reach points of possible completion in their utterances that correspond to the
places of transition-relevance, TRPs, where others could start to speak in attempts to
take a new turn of talk. The agent behaviours (acts), their internal states and procedures
are then described. The model is expanded with elaborate procedures for the resolution
of simultaneous talk, for speaking hesitations and their potential interruption, and for
the constraints of the different ‘sorts’ of utterance with respect to turn-taking: whether
the TRP is free, or the speaker has selected someone to speak next, has encouraged
anyone to speak, or has indicated the course of an extended multi-utterance turn at talk
as in sentence beginnings like “first of all,” or “let me tell you something:. . . ”.
The model and extensions are then comprehensively analysed through a series of large
quantitative evaluations computing various aggregate statistics such as: the total times
of single talk, multiple talk and silences; total occurrences of utterances, silences, simultaneous
talk, multiple starts, middle-of-utterance attempts at talking, false-starts,
abandoned utterances (interrupted by others), and more.